Field of the Invention
Embodiments of the invention relate to the field of circuit protection devices. More particularly, the present invention relates to a surge protection device with a thermal disconnect system configured to provide fast response to overheating.
Discussion of Related Art
Over-voltage protection devices are used to protect electronic circuits and components from damage due to over-voltage fault conditions. These over-voltage protection devices may include metal oxide varistors (MOVs) that are connected between the circuits to be protected and a ground line. MOVs have a unique current-voltage characteristic that allows them to be used to protect such circuits against catastrophic voltage surges. Typically, these devices utilize thermal links which can melt during an abnormal condition to form an open circuit. In particular, when a voltage that is larger than the nominal or threshold voltage is applied to the device, current flows through an MOV which generates heat. This causes the thermal link to melt. Once the link melts, an open circuit is created which prevents the over-voltage condition from damaging the circuit to be protected. However, these existing circuit protection devices do not provide an efficient heat transfer from the MOV to the thermal link, thereby delaying response times. In addition, existing circuit protection devices are complicated to assembly which increases manufacturing costs. Accordingly, it will be appreciated that improvements are desirable in present day circuit protection device employing metal oxide varistors.